I co-authored an article on MSDN.
Understanding WinFS by Exploring the WinFS Type System
by Thomas Rizzo and Sean Grimaldi
Microsoft Corporation

http://msdn.microsoft.com/Longhorn/understanding/pillars/WinFS/default.aspx?pull=/library/en-us/dnwinfs/html/winfs07142004.asp

Quite a few people seemed to like the article and gave it one of the highest ratings I have ever recieved on MSDN (8 out of 9 with 95 voters).

I am currently writing a new article with Thomas about querying WinFS. If there is anything you want to know about querying WinFS, or WinFS OPath, please let me know.